The Roles of Composition and Mesostructure of Cobalt‐Based Spinel Catalysts in Oxygen Evolution Reactions. Issue 68 (22nd October 2021)

• Record Type: Journal Article
• Authors: Rabe, Anna; Büker, Julia; Salamon, Soma; Koul, Adarsh; Hagemann, Ulrich; Landers, Joachim; Friedel Ortega, Klaus; Peng, Baoxiang; Muhler, Martin; Wende, Heiko; Schuhmann, Wolfgang; Behrens, Malte
• Is Part Of: Chemistry. Volume 27:Issue 68(2021)
• Page Start: 17038
• Page End: 17048
• Publication Date: 2021-10-22
• Subjects: cobalt spinels -- co-precipitation -- crystalline precursor decomposition approach -- oxygen evolution reaction -- structure-reactivity relationship; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202102400
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: By using the crystalline precursor decomposition approach and direct co‐precipitation the composition and mesostructure of cobalt‐based spinels can be controlled. A systematic substitution of cobalt with redox‐active iron and redox‐inactive magnesium and aluminum in a cobalt spinel with anisotropic particle morphology with a preferred 111 surface termination is presented, resulting in a substitution series including Co3 O4, MgCo2 O4, Co2 FeO4, Co2 AlO4 and CoFe2 O4 . The role of redox pairs in the spinels is investigated in chemical water oxidation by using ceric ammonium nitrate (CAN test), electrochemical oxygen evolution reaction (OER) and H2 O2 decomposition. Studying the effect of dominant surface termination, isotropic Co3 O4 and CoFe2 O4 catalysts with more or less spherical particles are compared to their anisotropic analogues. For CAN‐test and OER, Co 3+ plays the major role for high activity. In H2 O2 decomposition, Co 2+ reveals itself to be of major importance. Redox active cations in the structure enhance the catalytic activity in all reactions. A benefit of a predominant 111 surface termination depends on the cobalt oxidation state in the as‐prepared catalysts and the investigated reaction. Abstract : The particle anisotropy and cobalt content in spinel oxides is systematically varied and the impact on oxygen evolving reactions is investigated. For chemical and electrochemical water oxidation as well as H2 O2 decomposition the reactivity changes with the cobalt‐to‐metal ratio and the degree of anisotropy. Furthermore, the importance of the interplay of redox pairs and different active sites are highlighted.